Mineo I, Clarke P R, Sabina R L, Holmes E W
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
Mol Cell Biol. 1990 Oct;10(10):5271-8. doi: 10.1128/mcb.10.10.5271-5278.1990.
AMP deaminase (AMPD) is a central enzyme in eucaryotic energy metabolism, and tissue-specific as well as stage-specific isoforms are found in many vertebrates. This study demonstrates the AMPD1 gene product in rat is alternatively spliced. The second exon, a 12-base miniexon, was found to be excluded or included in a tissue-specific and stage-specific pattern. This example of cassette splicing utilizes a unique pathway through an RNA intermediate that generates an alternative 5' splice donor site at the point where exon 2 is ligated to exon 1. In the analogous intermediate of human AMPD1, the potential 5' splice donor site created at the boundary of exon 1 and exon 2 was a poor substrate for splicing because of differences in exon 2 sequences, and human AMPD1 was not alternatively spliced. These results demonstrate that in some cases alternative splicing may proceed through an RNA intermediate that generates an alternative splice donor site not present in the primary transcript. Discrimination between alternative 5' splice donor sites in the RNA intermediate of AMPD1 is apparently controlled by tissue-specific and stage-specific signals.
AMP脱氨酶（AMPD）是真核生物能量代谢中的一种关键酶，在许多脊椎动物中都发现了组织特异性和阶段特异性的同工型。本研究表明，大鼠中的AMPD1基因产物存在可变剪接。发现第二个外显子，一个12个碱基的小外显子，以组织特异性和阶段特异性模式被排除或包含。这种盒式剪接的例子利用了一条通过RNA中间体的独特途径，该途径在外显子2与外显子1连接的位点产生一个可变的5'剪接供体位点。在人类AMPD1的类似中间体中，由于外显子2序列的差异，在外显子1和外显子2边界处产生的潜在5'剪接供体位点是一个较差的剪接底物，并且人类AMPD1没有发生可变剪接。这些结果表明，在某些情况下，可变剪接可能通过一个RNA中间体进行，该中间体产生一个初级转录本中不存在的可变剪接供体位点。AMPD1的RNA中间体中可变5'剪接供体位点之间的区分显然受组织特异性和阶段特异性信号的控制。
